Exterior surface of a fence rail



FIG. 1 is a perspective view thereof;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken line showing of a horizontal internal support wall and opposing vertical channel walls is for illustrative purposes only and forms no part of the claimed design.

The drawings depict the design of section of a fence rail, and no limitations on length or size are intended thereby. 

I claim the ornamental design for an exterior surface of a fence rail, as shown and described. 